Process for preparing a monoalkyl aromatic

ABSTRACT

AN IMPROVEMENT IN A PROCESS WHEREIN A FIRST COMPOUND AND A SECOND COMPOUND REACT WITH EACH OTHER TO PRODUCE A THIRD COMPOUND AND A FOURTH COMPOUND IN ESSENTIALLY IRREVERSIBLE REACTIONS AND THE SECOND AND FOURTH COMPOUNDS REACT WITH EACH OTHER TO PRODUCE THE THIRD COMPOUND IN EQUILIBRIUM-LIMITED REACTIONS, THE SECOND COMPOUND BEING PRESENT IN THE REACTION MIXTURE IN EXCESS OF THAT REQUIRED FOR THE REACTIONS, AND THE EXCESS AMOUNT OF THE SECOND COMPOUND IS RECYCLED TO THE REACTION ZONE, WHICH INVOLVES REDUCING THE AMOUNT OF THE SECOND COMPOUND IN THE REACTION MIXTURE, INTRODUCING THEREIN THE FOURTH COMPOUND IN AN AMOUNT GREATER THAN WOULD BE PRESENT AT EQUILIBRIUM AND TERMINATING THE PROCESS BEFORE THE REACTION MIXTURE REACHES EQUILIBRIUM.

Dec. 11, 1973 DANIEL'Y. c. KO

PROCESS FOR PREPARING A MONOALKYL AROMATIC Filed Aug. 15, 1971 4 Sheets-Sheet l 0.03 0.04 LWf/ST GRAM 047m v57 HOUR/GRAM 0F 707A; F650 Dec. 11, 1973 DANIEL Y. c. KO

PROCESS FOR PREPARING A MONOALKYL AROMATIC FiledAug. 13, 1971 4 Sheets-Sheet 3 008 0./0 2 ,47 REACTOR- W457 232 c., CAP/1677') W 6 5 4 3 2 Qsxww QMQSQQQ km! 2% v6 ONE GRAM MOL (04/51/5/7/4/5 Fig. I

//\/l E/V7OR DAN/EL Y. C. K0

United States Patent 6 3,778,415 PROCESS FOR PREPARING A MONOALKYL ARGMATIC Daniel Y. C. K0, Pittsburgh, Pa., assignor to Gulf terminated when the amount of said undesired Compound I in the reaction product corresponds substantially in amount to the amount of said Compound I in the initial reaction mixture. By recycling the total amount of said Compound I in the reaction product, there is virtually no Researc Development Company Pittsburgh net production of the same. At the same time conver- Flled f kf g gg 171,541 sions of Compound F and selectively to desired Com- U S Cl 260672 T c Claims pound H is maintained.

' The process of this invention can further be illustrated by the following. Benzene and propylene were passed over 10 ABSTRACT OF THE DIS a zeollte catalyst, resulting 1n the product1on of cumene An improvement in a process wherein a first compound and P PY e- A Zeolite Catalyst cahhe hh and a second compound react with each other to produce as ahetllral f synthetle hydrated metal alumino-slllcate a third compound and a fourth compound in essentiauy cons1st1ng basically of an open, three-drmennoned frameirreversible reactions and the second and fourth com- Q 0f 4 h 0 trahedral, having a slllca to alupounds react with each other to produce the third commlna molar rat1o of at least about 3.0, a pore size large pound in equilibrium-limited reactions, the second comencugthto 83 l i s of bfnzene i pound being present in the reaction mixture 1n excess fzg an lp z f 3 aummicm g assoclatc of that required for the reactions, and the excess amount Y monova en Ions examp S0 or Po of the Second compound is recycled to the reaction Zone, slum, and the remainder with polyvalent cations, for exwhich involves reducing the amount of the second comample, lahthamlrh, cerlum, etc., and /or ammomum or pound in the reaction mixture introducing therein the hydrogen. part1cularly eifectrve zeohte 1s zeol1te Y such fourth compound in an amount greater than would be as dcfincd P 9 example i present at equilibrium and terminating the process before t c Y W111 fall wlthm the followmg chemlcal composl' the reaction mixture reaches equilibrium. 10m

This invention relates to a process wherein there oc- Wherein 3 generally has Value but c y froth curs essentially irreversible and equilibrium-limited reacto 111 the speclfic e h herelh a Y Zechtc Itions, illustrated, for example, by the following general molecular SleVe 0f the followlhg ulllt cell formula was reaction mechanisms: used:

-l- )8.8( 4)21.1( )8.3[ 2)55.7( 2)136.3]' Z and which had been previously heated to a temperature of LFGSH, about 550 C. for about one hour, with, presumably, the h f F H d I h 1 d loss of NH and H 0 therefrom. A one-half inch inner Wherelh eac an are c emlca F Q diameter, 52-inch long stainless steel reactor, equipped In the above reactions, for example, a react1on m1xture with a threednch by 50 ihch Outer jacket n with contalmng Compounds F and are reacted Wlth each dixylylethane as a heat transfer medium was used. Heat hatch cr contlfluous {Pcratlon, Yvlth Wlthout was supplied with a calrod electrical heater and was conl s 1h csscntlally lrrcvcl'slblc' reactlons to Produce trolled by a thermoelectric controller. A thermowell exsired Compound and undesged Compound I, wherei tended coaxially through the reactor. The temperature in the amount of 531d 60111291111 G lmtlauy Present 15 the reactor was measured by thermocouples evenly spaced eXceSS that cmcunt rcqulrcd for the reactl ons f through the preheat section, catalyst bed and support sec- III addltloh, e PP G {c t h f undesfred tion. The pressure was controlled by means of a pres- Compotlhd I esecntlany cqulhbnum'lmtltcd reactlons sure control valve in the efliuent line. Feed to the reactor to produce said des1red Compound H. During the course was pumped upflow by an adjustable Stroke proportion. of the reactlons the concentration of sald Compound I ting pump f a calibrated feed tank The reactor was ch amount cxccs? of h amount Present filled with a preheat section of glass beads to a depth of lei lll gl before the l'cactlon mlxture reaches 64111111) 14 inches. The catalyst section, 13 inches in depth, was composed of 10 grams of the specific 10 to 20 mesh Y 1 accordance Wlth the Process defined and clalmcd type zeolitic molecular sieve catalyst defined immediateherem, I have found that the total amount of recycle and 1 hereinabove with two volumes of 8 to 10 mesh quartz the S1Ze of the reactor he substantlallyfcduccd by per volume of the catalyst. The remaining reactor length d fi g e amollht 0f $a1d Compound G 111 the feactlcn was filled with glass beads. The efliuent from the reactor IIllXtllre, lnttodllclhg therelh p hf I 1I1 e11 amouht was cooled and collected in a gas-liquid separator. The greater than would be present at equlhbrlum and r off-gas was measured by a Wet test meter, While the liquid natmg the process before the reachon product reaches product was recovered and weighed. The results obtained equlhbrium. In a preferred embodlment, the process 1s are tabulated below in Table I.

TABLE I Run number 1 2 3 4 5 6 7 8 9 1o 11 Pressure, pounds per square inch au 0. 500 500 500 500 500 500 Temperature,C 232 232 232 214 214 214 3% 2 3% SS3 233 233 galllfiel g t o propylene molar ratio 0 0 0 0 o 0 9.96 9.96 5. 905 5.905 5. 905 5. 905 Reagantskifiaig$566555; 215 215 15 21 .0506 0. 0833 0. 01262 0.0267 0. 0515 0.1 enzene .2 1. 5 1.215 1. 215 1. 215 1.1733 1.1733 1.1733 1.17 3 P 1 0.122 .122 .1 Prodgtpg p ram 1 1027 01 m 01 (22 0 1:2 0 122 o 122 0.122 0.1986 0.1986 0.1986 0.1986

euzene 9 1.1 9 1.1065 1.1036 1.1023 1.066 0.

his one ass 0 -0 82. its; as. 0- O-tttg ttttt tit; Propylene 0. 0.0 0. 0.0 0.0 0.0 0.0 ri g 3 3 3 8 1 Liquid weight hourly space time= Gram catalyst hour/grams of total fluid. I Mole/100 grams of total fluid with total fluid including total reaction mixture.

Based on the above data the following reaction mechanism and kinetics were proposed:

k Benzene (B) Propylene (P) Cumene (C) Benzene 2 Propylene Diisopropyl Benzene (D) ks i2 I 1 B P: 2= 2 B P s= a n m and 4= 4 c wherein k k k and k; are reaction rate constants, r r r;, and r., are reaction rates (gram mols per hour per gram of catalyst) and C C C and C are concentrations (gram mols per gram of total fluid). The reaction mechanism and kinetics were mechanized on an analog computer. Simulation studies were then conducted to determine the rate constant and the associated activation energies so that the kinetic model represented the experimental data. Using the model so obtained simulated reactions were carried out on the computer wherein benzene was reacted with propylene to obtain cumene and diisopropyl benzene, using a benzene to propylene molar ratio of 4:1 and a temperature of 232 C. Concentration profiles for diisopropyl benzene for these runs are shown in FIG. I wherein the concentration of diisopropyl benzene in mols per mols of total fluid is plotted against liquid weight hourly space time. In FIG. I, R refers to the molar ratio of diisopropyl benzene to propylene in the initial reaction mixture. It can be seen how a small increase in diisopropyl benzene in the initial reaction mixture results in a significant saving in space time required. Space times of 0.065, 0.046 and 0.036 are needed for the cases of R =0.08, 0.10 and 0.12, respectively, to achieve 100 percent selectivity. In this case, a 47 percent reduction in space time is made possible by a small increase in diisopropyl benzene which results in only a 0.6 percent increase in total amount of material introduced into the reaction zone.

FIG. II shows the plot of the required space time to achieve 100 percent selectivity versus R with molar ratio of benzene to propylene (R as a parameter. Since a minimum R exists for each R any operation with less than a minimum R cannot achieve 100 percent selectivity. The minimum R increases as R decreases. The curves are asymptotic to the vertical lines crossing the minimum R s. The space time required decreased sharply as R was increased from the minimum R The decrease becomes less significant as R is further away from the minimum R This decreasing trend will continue until a point is reached beyond which complete conversion of propylene is no longer possible at the space time where 100 percent selectivity is achieved. Since complete conversion of propylene is a prerequisite herein, the basis of the curves shown in FIG. II is thus changed from 100 percent selectivity to 100 percent conversion of propylene. The latter parts of the curves are indicated by the dotted lines. Note that the dotted lines increase slightly as R increases for each R Thus, the minimum space time required for each R is obtained at the point where both 100 percent selectivity and 100 percent conversion of propylene are achieved at the same time.

It should be noted that at the same R the space time required decreases with increasing R This is due to the fact that with the same R the reactor conditions required to obtain 100 percent selectivity are further away from the inefiicient equilibrium region (minimum R region) at the higher R than at the lower R ratios.

Generally, space time required is a measure of the activity of the catalyst and of the efiiciency of the operation. However, a more important variable is the amount of catalyst needed, since catalyst is more directly related to the cost of a chemical operation. FIG. III shows the plot of the amount of catalyst required to achieve 100 percent selectivity versus R for several values of R Again it is seen that there is a minimum R for each R so that 100 percent selectivity is attainable only if Diisopropyl Benzene Benzene 2 Cumene R is greater than the minimum R If R is close to minimum, then the amount of catalyst needed is very large. By slightly increasing R tremendous saving of catalyst is achieved. The general trend of the catalyst required is the same as that of the space time required shown in FIG. II. At each value of R the catalyst amount decreases with increasing R until a point is reached beyond which complete conversion of propylene is not obtained at the space time where percent selectivity is achieved. The dotted lines, where 100 percent selectivity is also obtained, indicate the amount of catalyst required to completely convert propylene. As noted, the dotted lines rise very slightly as R increases, since such a small increase of diisopropyl benzene can only have minimal eifects on the alkylation activity. However, there is a significant difference between the space time needed and the catalyst required. At the same R the amount of catalyst at higher R is not necessarily smaller than for for lower R Examination of FIG. HI reveals that there is a minimum amount of catalyst needed to achieve 100 percent selectivity for each R In fact, an envelope in FIG. III defines the unique combination of R and R so that 100 percent selectivity can be obtained with the least amount of catalyst. The functional relationship between the least amount of catalyst and R is plotted on FIG. IV. It is seen that the least amount of catalyst required decreases With R For the most efficient operation, at least twice as much catalyst is required for a benzene/propylene molar ratio of 10:1 as is required at 3:1. This is totally unexpected and unique because it is directly contrary to the design and operating principles of conventional cumene processes.

Separation and pumping costs (investment and operating costs) are directly related to the total recycle flow fate. FIG. V shows the total recycle flow rate versus R for three values of R The amount of catalyst is also plotted for reference. At each value of R total recycle flow rate increases with increasing R However, the increase is very small because the increased amount of diisopropyl benzene constitutes a very small percentage of the total recycle flow. A much more noticeable reduction in total recycle fiow can be made by reducing R The important indication in FIG. V, however, is that the objective can be realized by reducing both the amount of catalyst and the total recycle flow rate.

Finally, as an example to show the significance of the unusual discovery made herein, a comparison is made for points A and B in FIG. HI where 100 percent selectivity to cumene is obtained. Point A represents the condition of R =10, R =0.25, liquid weight hour space time (LWHST)-=0.094, 78 grams of catalyst and total recycle flow rate of 826 grams per unit time (total diisopropyl benzene and benzene in excess of the amount needed for reaction of benzene with propylene), while point B conditions are R =3, R =0.15, LWHST=0.044, 13 grams of catalyst and total recycle flow rate of grams per unit time. Thus, at point B the catalyst requirement is only /6 of that needed at point A. The plant size of point B, as measured by flow rate, as above defined, is reduced to about Vs of that needed at point A. Thus, contrary to the conventional cumene process, we can reduce the benzene-to-propylene ratio and increase the space velocity while introducing the appropriate amount of diisopropyl benzene so that 100 percent selectivity to cumene is achieved most efliiciently.

As an illustration of the operation of the process defined and claimed herein, benzene is generally reacted with propylene in a molar ratio of about 2:1 to about 15:1, preferably about 5:1 to about 10:1, at a temperature of about to about 260 C., preferably about 200 to about 235 C., and a pressure of about 350 to about 70 pounds per square inch gauge, preferably about 400 to about 550 pounds per square inch gauge, at an LWHST of about 0.03 to about 1.0, preferably about 0.04 to about 0.5 to produce as product cumene and diisopropyl benzene, with the latter, at equilibrium, amounting to about 0.01 to about 0.15 mol percent thereof, preferably from about 0.03 to about 0.08 mol percent, based on the product. In the practice of this invention the unreacted benzene is recycled but the molar ratio of benzene to propylene at the inlet line of the reactor has been reduced to about 1:1 to about :1, preferably to about 2:1 to about 6:1. The amount of diisopropyl benzene also introduced therein amounts to about 0.2 to about 10 mol percent, preferably from about 0.5 to about 5.0 mol percent, based on the total mols of incoming feed. The reaction is terminated prior to equilibrium and preferably when the amount of diisopropyl benzene therein is equal to the amount introduced into the reaction mixture. In a preferred embodiment, in order to obtain no net production of diisopropyl benzene, the diisopropyl benzene is recovered from the reaction product and is recycled so that it constitutes the diisopropyl benzene introduced into the reaction mixture.

The improvement herein has been both broadly and specifically described and defined, but it is apparent that the same is applicable to any process wherein there occurs essentially irreversible and equilibrium-limited reactions, as exemplified by the general reaction mechanisms defined above, for example, alkylation reactions, such as the alkylation of benzene with propylene or ethylene to obtain cumene or ethyl benzene, respectively, as desired compounds and diisopropyl benzene or diethyl benzene, respectively, as undesired compounds, or the alkylation of toluene with propylene to obtain cymene as the desired compound and diisopropyl toluene as the undesired compound, dealkylation reactions, such as the reaction of toluene with hydrogen at elevated temperatures to obtain benzene as the desired compound and diphenyl as the undesired compound, etc.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a process wherein an olefin and an aromatic hydrocarbon react with each other to produce a monoalkyl aromatic and a dialkyl aromatic in essentially irreversible reactions and said monoalkyl aromatic and dialkyl aromatic react with each other to produce said monoalkyl aromatic in equilibrium-limited reactions, said aromatic hydrocarbon being present in the reaction mixture in excess of that required for the reactions, and the excess amount of said aromatic hydrocarbon is recycled to the reaction zone, during the course of said reactions the concentration of said dialkyl aromatic reaches an amount in excess of that amount present at equilibrium before the reaction mixture reaches equilibrium, the improvement which comprises reducing the amount of said excess aromatic hydrocarbon in the initial reaction mixture, introducing therein said dialkyl aromatic in an amount greater than would be present at equilibrium and terminating the reaction before the reaction mixture reaches equilibrium.

2. The process of claim 1 wherein the amount of dialkyl aromatic in the reaction product upon termination of the reaction corresponds substantially to the amount of said dialkyl aromatic initially added into the reaction zone.

3. The process of claim 2 wherein said dialkyl aromatic in the reaction product is recycled to the reaction zone.

4. The process of claim 1 wherein said olefin is propylene, said aromatic hydrocarbon is benzene, said monoalkyl aromatic is cumene and said dialkyl aromatic is diisopropyl benzene.

5. The process of claim 4 wherein the amount of diisopropyl benzene upon termination of the reaction corresponds substantially to the amount of diisopropyl benzene initially added to the reaction zone.

6. The procms of claim 5 wherein the diisopropyl benzene in the reaction product is recycled to the reaction zone.

7. The process of claim 4 wherein the molar ratio of benzene to propylene into the reactor is from about 1:1 to about 10:1 and the amount of diisopropyl benzene introduced amounts to about 0.2 to about 10 mol percent, based on the total mols of incoming feed.

8. The process of claim 4 wherein the molar ratio of benzene to propylene into the reactor is from about 2:1 to about 6:1 and the amount of diisopropyl benzene introduced amounts to about 0.5 to about 5.0 mol percent, based on the total mols of incoming feed.

9. The process of claim 4 wherein the reactants are benzene and propylene and are present in a molar ratio of about 2:1 to about 15:1, the reaction temperature is about to about 260 C. and the pressure about 350 to about 700 pounds per square inch gauge.

10. The process of claim 4 wherein the reactants are benzene and propylene and are present in a molar ratio of about 5:1 to about 10:1, the reaction temperature is about 200 to about 235 C. and the pressure about 400 to about 550 pounds per square inch gauge.

References Cited UNITED STATES PATENTS 2,403,785 7/1946 Britton et a1 260-671 R 2,818,452 12/1957 Mavity 260-671 P 2,995,611 8/1961 Linn et a1 260-671 R 2,883,438 4/1959 Egbert 260-671 P 2,920,118 4/ 1960 Landau et a1. 260-671 P 3,274,278 9/ 1966 Kapur et a1 260-671 B 3,385,906 5/1968' Kaufman 260-671 P OTHER REFERENCES Hougen et al., Chemical Process Principles, Part II, 2nd edition, John Wiley & Sons, New York (1954), pp. 1020-1.

CURTIS R. DAVIS, Primary Examiner US. Cl. X.R. 260-671 P po-wso UNITED STATES PATENT OFFICE 56 CERTIFICATE OF CORRECTION Patent No. 3, 778,415 a e December 11, 1973 Inventor(s) I I Daniel Y. C. K0 I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column '2, line 28, "zeolite" should be "zeolitic".

Column 2, Table I, under Run No. 11, 0.007"

should be 0.0073".

Column 4, line 35, "fate" should be "rate".

Column 4, line 72, "70" I should be "700".

Signed and sealed this 23rd day of April 19714..

(SEAL) Attest:

EDWARD I-l.l'LETGilER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

